If we have one extensible mechanism to cover many important use cases, I don't think two flags are too luxury. I think HBH and E2E are indeed two distinct requirements and for the efficiency of packet processing, they should be taken care of separately.
Haoyu -----Original Message----- From: Yangfan (IP Standard) <[email protected]> Sent: Thursday, July 15, 2021 6:10 AM To: Haoyu Song <[email protected]>; spring <[email protected]> Subject: 答复: I-D Action: draft-yang-spring-ach6-sr-00.txt Hi Haoyu, Thank you for your comments. In the draft I propose two approaches of ACH6 encapsulation, one is in IPv6 DOH EH, another is in payload as you said. To encap ACH6 message in payload and use SRH flag to indicate the processing has its advantages. 1) ACH6 packet encapsulated in payload would never get lost 2) friendly to present implementations. But I doubt that ACH6 may need two different flags to indicate whether intermediate node should process it or not. In draft-~-siam, T flag indicates every SR endpoint to process IOAM data. It is not necessary for every SR endpoint to process ACH6 packet if this packet is only e2e used. It might be too luxurious to be considered as an option. :) Best regards, Fan -----邮件原件----- 发件人: spring [mailto:[email protected]] 代表 Haoyu Song 发送时间: 2021年7月15日 0:47 收件人: Yangfan (IP Standard) <[email protected]>; spring <[email protected]> 主题: Re: [spring] I-D Action: draft-yang-spring-ach6-sr-00.txt Dear authors, I like the idea of ACH for SRv6, and I think the use cases make sense and expect to see more if such mechanism exists. However, my opinion is that, since ACH packets are dedicated control packets, it might be easier to encapsulate it in UDP payload while using an SRH flag to indicate the presence of ACH, which is more extensible. In fact, I think this draft can be consolidated with our draft "draft-song-spring-siam-01" for supporting IOAM ins SRv6 https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-song-spring-siam-01&data=04%7C01%7Chaoyu.song%40futurewei.com%7C58fe8ca575554e33fb4108d94791cdb8%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637619513822819814%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=eDkM9JCqsN%2FgIUaLg00PRy%2F1WOAg%2FrznagwtejcYtn8%3D&reserved=0 because I can see the potential for ACH6 to become a generic mechanism in SRv6 to support OAM and message passing pertaining to specific SR paths. Look forward more discussions on this! Best, Haoyu -----Original Message----- From: spring <[email protected]> On Behalf Of Yangfan (IP Standard) Sent: Monday, July 12, 2021 7:32 PM To: spring <[email protected]> Subject: [spring] I-D Action: draft-yang-spring-ach6-sr-00.txt Hi SPRING， A new draft was submitted to specify how an ACH6 (associated channel over IPv6) control channel is used in a Segment Routing network. On one hand, SRv6 SIDs list in SRH provides a certain SRv6 path. On the other hand, ACH6 provides the control and management capability to the SRv6 path. Here is some background info if you are not acquainted with ACH6, ACH6 is initially proposed at IETF 110 (https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-yang-rtgwg-ipv6-associated-channel-01&data=04%7C01%7Chaoyu.song%40futurewei.com%7C58fe8ca575554e33fb4108d94791cdb8%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637619513822819814%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=lw40XWM%2Btq2bsaHTIEBsfSrTZ95TGTwVrn6ahrrFjKE%3D&reserved=0) ACH6 in SR (https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-yang-spring-ach6-sr&data=04%7C01%7Chaoyu.song%40futurewei.com%7C58fe8ca575554e33fb4108d94791cdb8%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637619513822819814%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=eYmH1dL0tlgZNeeWktSencVDQ8Y09H6mh6C3wuUxtp0%3D&reserved=0) and ACH6 OAM mechanism in SR (https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-yang-spring-ach6-oam-sr&data=04%7C01%7Chaoyu.song%40futurewei.com%7C58fe8ca575554e33fb4108d94791cdb8%7C0fee8ff2a3b240189c753a1d5591fedc%7C1%7C0%7C637619513822829767%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=tvcmpAIfiQ3eoPzJoa0ZDtGgXHhX42z0ZHWESx610T8%3D&reserved=0) are proposed at IETF 111 As always, comments and suggestions are welcome and appreciated. Stay safe. Best regards, Fan (on behalf of authors) -----邮件原件----- 发件人: I-D-Announce [mailto:[email protected]] 代表 [email protected] 发送时间: 2021年7月13日 0:14 收件人: [email protected] 主题: I-D Action: draft-yang-spring-ach6-sr-00.txt A New Internet-Draft is available from the on-line Internet-Drafts directories. Title : ACH6 in Segment Routing Authors : Fan Yang Tianran Zhou Filename : draft-yang-spring-ach6-sr-00.txt Pages : 11 Date : 2021-07-12 Abstract: Associated Channel over IPv6 (ACH6) provides a control channel to one specific IPv6 forwarding path for control and management purpose. When ACH6 is used in a Segment Routing network, it provides a control channel to an SRv6 path. This document specifies an SRv6 ACH6 mechanism and describes how ACH6 is applied in a Segment Routing network. 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